Between rush hour traffic and 18-wheelers, our roads take a real beating over time. Tiny sensors in the asphalt could give us a real time map of stress on ageing roads, but then how do you keep embedded sensors powered for years? By harnessing the very motion of the cars whizzing by.
That's the clever idea the Federal Highway Administration is now putting to the test. It's recently awarded two grants to Nizar Lajnef, an engineering professor at the Michigan State University, to test a square-millimetre sized piezoelectric sensor that detects stress and strain vibrations in highways. Since roads, bridges and highways can start deteriorating even before visible cracks show up, the sensors could keep a much closer eye on our infrastructure.
Piezoelectric materials accumulate electric charge with mechanical stress, essentially turning the thump-thump of cars into power. Each sensor is off until "woken up" by vibrations in the road, so it doesn't waste electricity during long, empty stretches. It can then record several hours of data that are retrievable wirelessly via radio.
Currently, battery-powered devices last only two or three years, and digging up perfectly good roads to replace is totally impractical. Another option, wired sensors, makes building these roads a good deal more complicated. These piezoelectric sensors could be simply dropped into the concrete as roads are poured, which is exactly how the researchers plan test them. Soon you could be driving on car-powered smartroads of the future. [Engineering News-Record]